/**
 * @program: LeetCode
 * @description: LeetCode : 剑指 Offer II 062. 实现前缀树
 * @author: WXY
 * @create: 2023-01-07 09:15
 * @Version 1.0
 **/
public class offer_twentyone1_Trie {
    class Trie {
        private Trie[] children;
        private boolean isEnd;

        public Trie() {
            children = new Trie[26];
            isEnd = false;
        }

        public void insert(String word) {
            Trie node = this;
            for (int i = 0; i < word.length(); i++) {
                char ch = word.charAt(i);
                int index = ch - 'a';
                if (node.children[index] == null) {
                    node.children[index] = new Trie();
                }
                node = node.children[index];
            }
            node.isEnd = true;
        }

        public boolean search(String word) {
            Trie node = searchPrefix(word);
            return node != null && node.isEnd;
        }

        public boolean startsWith(String prefix) {
            return searchPrefix(prefix) != null;
        }

        private Trie searchPrefix(String prefix) {
            Trie node = this;
            for (int i = 0; i < prefix.length(); i++) {
                char ch = prefix.charAt(i);
                int index = ch - 'a';
                if (node.children[index] == null) {
                    return null;
                }
                node = node.children[index];
            }
            return node;
        }

    }
}
